There are many known methods and apparatus for reclaiming germanium (Ge) from chemical vapor deposition (CVD) exhaust.
For example, U.S. Pat. No. 4,385,915 describes a batch process for the removal of germanium (Ge) from an effluent that is the result of processes used for the production of optical components. In the batch process, optical fiber reactors provide effluent to scrubbers, which processes the effluent and provides a basic aqueous output to a moving sandbag filter. A filtered aqueous medium having dissolved germanium is precipitated from a medium provided by the moving sandbag filter by a precipitator by the addition of a precipitating agent such as an aqueous magnesium sulfate solution. The process also includes providing the filtered aqueous medium to a holding tank, where a sodium hydroxide solution is added to bring the pH of the aqueous medium therein to a value of twelve, and recycling a medium back to the scrubbers for reprocessing. One problem with this process is that it is a batch process, and thus not continuous. Another problem is that the basic aqueous output from the scrubber is filtered before being equalized, neutralized, or the hypochlorites are reduced.
Other methods and apparatus for reclaiming germanium (Ge) from chemical vapor deposition (CVD) exhaust include the following: U.S. Pat. No. 2,827,361 describes a method of recovering germanium (Ge) which involves removing dissolved silicon contained in an aqueous solution having dissolved germanium (Ge) therein and having a pH value of at least seven. The method includes the step of adding soluble inorganic aluminum to the solution to precipitate insoluble silicon from the solution. The aqueous solution used is aqueous sodium hydroxide. U.S. Pat. No. 2,929,677 describes a process for recovering germanium (Ge) from zinc oxide fume taken from furnace slag, using an aqueous sodium hydroxide solution to precipitate iron and germanium (Ge). U.S. Pat. No. 4,367,085 describes a method of making optical fiber preforms using glass raw material gases. The apparatus used in the method includes an exhaust gas cleaner to process the gases exiting the exhaust port. The cleaning process apparently includes the use of a water spray and a neutralizer, such as sodium hydroxide (NaOH). U.S. Pat. No. 4,578,253 describes a method of recovering germanium (Ge) from the effluent of a vapor deposition process of making an optical fiber. This patent incorporates methods disclosed in the U.S. Pat. No. 4,385,915. DE Patent No. 3,143,958 describes a method of forming optical fibers which includes steps of reclaiming the gases used as dopants. A water spray and fractional distillation process are used in the method of recovering germanium (Ge) for reuse.
Moreover, FIG. 1 of the present patent application shows a known continuous stirred tank reactor for waste treatment which includes the following steps: Providing a tube exhaust from a CVD lathes to a scrubber having a recirculation pump; scrubbing the tube exhaust and passing liquid waste from the scrubber to a pH neutralization reactor; combining the liquid waste with a polyflow, a water bath and a scrubber overclad, and providing a pH neutralization solution to a settling stage; providing a slurry to a filtration stage, which provides a filtered slurry back to the settling stage; and providing the slurry to a filter press which provides filter cakes for disposing in a landfill.